Evaluation of alternative means to control postharvest Rhizopus rot of peaches

- Calcium chloride and lemongrass oil were evaluated against Rhizopus rot on peaches.
- A complete R. stolonifer inhibition was observed at 1.5 ml/l and 20 g/l for lemongrass and calcium chloride, respectively.
- In vivo a significant reduction of both rot incidence and severity was achieved using lemongrass oil at 1.5 ml/l and calcium chloride at 1.5 g/l.
- The combination of the treatments gave the best performance against the rot.
- The microscopic observation using SEM showed morphological alterations.

The objective of the present research was to test the activity of calcium chloride and lemongrass oil, alone or in combination, against Rhizopus stolonifer on peaches. The inhibitory effect was evaluated both in vitro and in vivo. Results showed that in vitro pathogen growth decreased as treatment's concentration increased, reaching a complete inhibition at 1.5 ml/l and 20 g/l for lemongrass and calcium chloride, respectively. However, taking into account phytotoxicity phenomena, lower concentrations were tested in vivo. A 70% reduction of both rot incidence and severity was achieved using lemongrass oil at 1.5 ml/l; whereas, in presence of CaCl2, the disease reduction was much lower, reaching a maximum at 1.5 g/l of 30 and 59% for incidence and severity, respectively. The combination of the two treatments gave the best performance against rot, and the control effect proved to be synergic as far as disease severity concerns. The observation using scanning electron microscopy (SEM) confirmed the ultra-structure modification in R. stolonifer after treatment. New strategies are needed to reach the critical goal of controlling Rhizopus rot of peaches with no fungicide residues on fruit. In this context, the integration of calcium chloride with lemongrass essential oil might be promising, although further trials are needed.